thanks for your reply. I switched off the AGC-Function in SDR Uno but it seems its doing some kind of AGC anyway when crossing the Filter Boundaries cause the RF-Gain Slider is changing by its own.

So my test was not valid i think.

Regards Robert

Hi Robert

The AGC button on SDRuno is not the IF AGC, it controls the output level. You need to turn of the IF AGC and set the IF gain manually. The RF Gain Reduction control is used to set the gain/attenuation for the LNA.

One thing to bear in mind is that the RSP module will be changing various settings as a sweep crosses a band boundary, and there will be a change in noise level displayed. This change will not be seen when using SDRuno because it is not changing frequencies in order to cover the displayed spectrum. Using manual gain control, IF at 59dB and RF Gain Reduction slider at the bottom, I see a noise floor difference of around 15dB when changing from 419 to 420MHZ. The level difference will change from band to band, and probably between devices as well. Let me know how it goes.

I forgot to mention: If you experiment with the IF gain and the RF Gain Reduction controls, you will see how the various gain settings affect the noise floor level. With the analyser, the IF and RF gains are set according to the selected reference level. HIgher reference levels will result in reduced gain, and higher noise floors.

I made a tracking generator from the information provided in the documentation with an AD9959.
Here are my remarks:
- contrary to what the documentation says the command sent by the analyser in "spot mode" is "dds" and not "SPOTF"
- the spot frequency is limited to 90 MHz, is it possible to have a mode other than AD9850 or 9851 that does not have this limitation?
- the STEPTIME time is always equal to 20 ms is this normal?
- There is no synchronization between the display (receiver) and the generator which makes it unusable.
how should synchronization be done?

papyblue wrote: contrary to what the documentation says the command sent by the analyser in "spot mode" is "dds" and not "SPOTF"

HI

Either will work, "DDS" was used on an older version of the firmware and the command has not been updated.

papyblue wrote:the spot frequency is limited to 90 MHz, is it possible to have a mode other than AD9850 or 9851 that does not have this limitation?

Yes, the updated version allows for a "Custom" type. The Custom type will place no frequency limits on what is send to youre code.

papyblue wrote: the STEPTIME time is always equal to 20 ms is this normal?

Currently, yes. I have to add a control to the Trackgen control panel to allow the stepping time to be set.

papyblue wrote:here is no synchronization between the display (receiver) and the generator which makes it unusable.
how should synchronization be done?

Correct, currently there is no synchronization. Once the analyser is running and your frequency and span settings are as you want them, select
"Peak" mode for the trace you are using. The DDS output will appear as a series of spikes which can be highlighted by enabling the markers system and then enabling the peak finder system. This link shows what can be done. Sync is being looked into, but in the meantime it is quiet usable.

One of my applications for using the RSP spectrum analyser is looking for spurious outputs of an SDR transmitter. Especially for the higher spans of 500 MHz -1 GHZ – 2 GHz there are so many high-level clock spurious of the RSP-Duo, with n*24 MHz, that it is hard to recognise any spurious of my own input signal.
Because I could not remember seeing such high clock spurious in SDR Uno I made a comparison between SDR Uno and the RSP Spectrum Analyser. Using a LImeSDR I generated a -60 dBm signal at 600.05 MHz and measured the level of this signal and the level of the of the 25th harmonic of the 24 MHz clock at 600 MHz. I chose similar settings for both programs

uno_sig-60dBm.jpg (261.38 KiB) Viewed 5168 times

sa_sig_m60dbm.jpg (222.38 KiB) Viewed 5168 times

The results show a big difference. In SDR Uno the clockspur at 600 MHz is at -98 dB. In the RSP Spectrum Analyser with 50 dBm Ref level the LimeSDR input is measured with –65.4 dBm but the 600 MHz clock spurious is measured at -51.9 dBm, that is 46 dB stronger than in SDR Uno. Similar results with other Ref levels.
Also, the RSP Spectrum Analyser output shows a lot of low-level spurious signals, that are not visible in SDR Uno.
Maybe a possible reason is that the spectrum analyser has allocated more of its gain after the circuit parts where the clock spur is coupled in and that SDR Uno has its gain more before those parts?

Another point that I mentioned before is that after selecting tuner 1 in the output screen I see a mix of the signals that are connected to both tuner inputs. The output level of the “wrong” output signal corresponding to the tuner2 input is so high that it can’t be just coupling from tuner 2 input to the tuner 1 circuit. The only possible reason that comes to my mind is that the multiplexed output signals of tuner 1 and tuner 2 are not demultiplexed in the correct way.

Hope you find a solution for this problem because I really like the RSP Program.

I just installed version 1.0 Alpha on my Surface Pro 3 running Windows 10 Pro and am using the RSP1A receiver. The app installed fine and seems to run fine. I am comparing the app with my Siglent SSA-3021X spectrum analyzer. Very impressive for an alpha version. I was able to use a -1.8 ppm trim to put the RSP1A on frequency and a dbm Trim of 1.4 to calibrate the db scale. Using my HP 8648D signal generator, the app tracks very accurately be -120 dbm and -20 dbm. On my box, the unit goes into ADC overload with an input level of -28 dbm.

I would like to do some oscillator phase noise measurements and convert the signal reading to dBc/Hz. What is the RBW of the app or what conversion factor should I use?